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All Places > Dallas User Group > Blog > 2016 > November

I've been seeing a lot of posts asking about main vs. subdomain usage in Marketo so I decided to ask a friend and expert in this field to elaborate. Sharing his guest blog here.


The part I was most interested in.


Questions that Marketo folks struggle with



Should they purchase a dedicated IP to build out the subdomain’s reputation even if they are small?

A dedicated IP for a low-volume sender could actually hurt someone’s deliverability as they will never be able to establish a reputation. I normally recommend around 500,000 sends per month to have a dedicated IP.


I do have 1 client on Marketo that sends out 100,000 emails a month (all B2B) on a dedicated IP. The only reason is that their are an international sender and the majority of the networks they send to required a dedicated IP to whitelist.

Agree on the subdomain reputation too. Gmail/Google Apps, along with others are now looking at the subdomain to determine reputation. Each mail stream and sending

platform should use a different subdomain when sending out email or else you could “cross contaminate” the reputation.





When it comes to using a third party like Marketo on a shared server, how do we get affected if someone else on the same server has bad email practices?

Shared IP pools can be problematic if not managed properly. If you have a client on a shared IP pool, other senders on that pool will affect your deliverability. If a sender on the shared IP pool land on a blacklist, that affects all others on that pool. Not to mention if an ISP or network blocks the IP, mail traffic is affected for all senders. Keeping an eye out for blocks, soft bounces, blacklists, etc. can help catch these issues quicker.


It is very important to ask any email service provider about the other senders on the shared IP pool, like:



How many other senders are on the shared IP pool?


What is the typical daily, monthly volume on the shared IP pool?


How many IPs are in the shared IP pool?


What categories or lines of business comprise the shared IP pool?